use Data::Dumper;
use List::Util qw(first);

my @x = ({"aaa" => 100});

say Dumper([grep { $_->{"aaa"} < 4 } @x]->[0]);
say Dumper((first { $_->{"aaa"} < 4 } @x));

##</code><code>##

$VAR1 = undef;

$VAR1 = undef;

##</code><code>##

say Dumper([grep { $_->{"aaa"} < 4 } @x]->[0]->{"aaa"});
say Dumper((first { $_->{"aaa"} < 4 } @x)->{"aaa"});

##</code><code>##

$VAR1 = undef;

Can't use an undefined value as a HASH reference at test.pl line 7.